/**
 * @file
 * TCP internal implementations (do not use in application code)
 */

/*
 * Copyright (c) 2001-2004 Swedish Institute of Computer Science.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
 * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
 * OF SUCH DAMAGE.
 *
 * This file is part of the lwIP TCP/IP stack.
 *
 * Author: Adam Dunkels <adam@sics.se>
 *
 */
#ifndef LWIP_HDR_TCP_PRIV_H
#define LWIP_HDR_TCP_PRIV_H

#include "lwip/opt.h"

#if LWIP_TCP /* don't build if not configured for use in lwipopts.h */

#include "lwip/tcp.h"
#include "lwip/mem.h"
#include "lwip/pbuf.h"
#include "lwip/ip.h"
#include "lwip/icmp.h"
#include "lwip/err.h"
#include "lwip/ip6.h"
#include "lwip/ip6_addr.h"
#include "lwip/prot/tcp.h"

#ifdef __cplusplus
extern "C"
{
#endif

    /* Functions for interfacing with TCP: */

    /* Lower layer interface to TCP: */
    void tcp_init(void); /* Initialize this module. */
    void tcp_tmr(void);  /* Must be called every
                            TCP_TMR_INTERVAL
                            ms. (Typically 250 ms). */
    /* It is also possible to call these two functions at the right
       intervals (instead of calling tcp_tmr()). */
    void tcp_slowtmr(void);
    void tcp_fasttmr(void);

    /* Call this from a netif driver (watch out for threading issues!) that has
       returned a memory error on transmit and now has free buffers to send more.
       This iterates all active pcbs that had an error and tries to call
       tcp_output, so use this with care as it might slow down the system. */
    void tcp_txnow(void);

    /* Only used by IP to pass a TCP segment to TCP: */
    void tcp_input(struct pbuf* p, struct netif* inp);
    /* Used within the TCP code only: */
    struct tcp_pcb* tcp_alloc(u8_t prio);
    void tcp_free(struct tcp_pcb* pcb);
    void tcp_abandon(struct tcp_pcb* pcb, int reset);
    err_t tcp_send_empty_ack(struct tcp_pcb* pcb);
#if LWIP_TCP_TC8_EMPTY_ACK
    err_t tcp_send_empty_ack_used_last_seq(struct tcp_pcb* pcb);
#endif /* LWIP_TCP_TC8_EMPTY_ACK */
    err_t tcp_rexmit(struct tcp_pcb* pcb);
    err_t tcp_rexmit_rto_prepare(struct tcp_pcb* pcb);
    void tcp_rexmit_rto_commit(struct tcp_pcb* pcb);
    void tcp_rexmit_rto(struct tcp_pcb* pcb);
    void tcp_rexmit_fast(struct tcp_pcb* pcb);
    u32_t tcp_update_rcv_ann_wnd(struct tcp_pcb* pcb);
    err_t tcp_process_refused_data(struct tcp_pcb* pcb);

/**
 * This is the Nagle algorithm: try to combine user data to send as few TCP
 * segments as possible. Only send if
 * - no previously transmitted data on the connection remains unacknowledged or
 * - the TF_NODELAY flag is set (nagle algorithm turned off for this pcb) or
 * - the only unsent segment is at least pcb->mss bytes long (or there is more
 *   than one unsent segment - with lwIP, this can happen although unsent->len < mss)
 * - or if we are in fast-retransmit (TF_INFR)
 */
#define tcp_do_output_nagle(tpcb)                                                                               \
    ((((tpcb)->unacked == NULL) || ((tpcb)->flags & (TF_NODELAY | TF_INFR))                                     \
      || (((tpcb)->unsent != NULL) && (((tpcb)->unsent->next != NULL) || ((tpcb)->unsent->len >= (tpcb)->mss))) \
      || ((tcp_sndbuf(tpcb) == 0) || (tcp_sndqueuelen(tpcb) >= TCP_SND_QUEUELEN)))                              \
         ? 1                                                                                                    \
         : 0)
#define tcp_output_nagle(tpcb) (tcp_do_output_nagle(tpcb) ? tcp_output(tpcb) : ERR_OK)

#define TCP_SEQ_LT(a, b)       ((s32_t)((u32_t)(a) - (u32_t)(b)) < 0)
#define TCP_SEQ_LEQ(a, b)      ((s32_t)((u32_t)(a) - (u32_t)(b)) <= 0)
#define TCP_SEQ_GT(a, b)       ((s32_t)((u32_t)(a) - (u32_t)(b)) > 0)
#define TCP_SEQ_GEQ(a, b)      ((s32_t)((u32_t)(a) - (u32_t)(b)) >= 0)
/* is b<=a<=c? */
#if 0 /* see bug #10548 */
#define TCP_SEQ_BETWEEN(a, b, c) ((c) - (b) >= (a) - (b))
#endif
#define TCP_SEQ_BETWEEN(a, b, c) (TCP_SEQ_GEQ(a, b) && TCP_SEQ_LEQ(a, c))

#ifndef TCP_TMR_INTERVAL
#define TCP_TMR_INTERVAL 250 /* The TCP timer interval in milliseconds. */
#endif                       /* TCP_TMR_INTERVAL */

#ifndef TCP_FAST_INTERVAL
#define TCP_FAST_INTERVAL TCP_TMR_INTERVAL /* the fine grained timeout in milliseconds */
#endif                                     /* TCP_FAST_INTERVAL */

#ifndef TCP_SLOW_INTERVAL
#define TCP_SLOW_INTERVAL (2 * TCP_TMR_INTERVAL) /* the coarse grained timeout in milliseconds */
#endif                                           /* TCP_SLOW_INTERVAL */

#define TCP_FIN_WAIT_TIMEOUT 20000 /* milliseconds */
#define TCP_SYN_RCVD_TIMEOUT 20000 /* milliseconds */

#define TCP_OOSEQ_TIMEOUT    6U /* x RTO */

#ifndef TCP_MSL
#define TCP_MSL 60000UL /* The maximum segment lifetime in milliseconds */
#endif

/* Keepalive values, compliant with RFC 1122. Don't change this unless you know what you're doing */
#ifndef TCP_KEEPIDLE_DEFAULT
#define TCP_KEEPIDLE_DEFAULT 7200000UL /* Default KEEPALIVE timer in milliseconds */
#endif

#ifndef TCP_KEEPINTVL_DEFAULT
#define TCP_KEEPINTVL_DEFAULT 75000UL /* Default Time between KEEPALIVE probes in milliseconds */
#endif

#ifndef TCP_KEEPCNT_DEFAULT
#define TCP_KEEPCNT_DEFAULT 9U /* Default Counter for KEEPALIVE probes */
#endif

#define TCP_MAXIDLE     TCP_KEEPCNT_DEFAULT* TCP_KEEPINTVL_DEFAULT /* Maximum KEEPALIVE probe time */

#define TCP_TCPLEN(seg) ((seg)->len + (((TCPH_FLAGS((seg)->tcphdr) & (TCP_FIN | TCP_SYN)) != 0) ? 1U : 0U))

/** Flags used on input processing, not on pcb->flags
 */
#define TF_RESET   (u8_t)0x08U /* Connection was reset. */
#define TF_CLOSED  (u8_t)0x10U /* Connection was successfully closed. */
#define TF_GOT_FIN (u8_t)0x20U /* Connection was closed by the remote end. */

#if LWIP_EVENT_API

#define TCP_EVENT_ACCEPT(lpcb, pcb, arg, err, ret) ret = lwip_tcp_event(arg, (pcb), LWIP_EVENT_ACCEPT, NULL, 0, err)
#define TCP_EVENT_SENT(pcb, space, ret) \
    ret = lwip_tcp_event((pcb)->callback_arg, (pcb), LWIP_EVENT_SENT, NULL, space, ERR_OK)
#define TCP_EVENT_RECV(pcb, p, err, ret) \
    ret = lwip_tcp_event((pcb)->callback_arg, (pcb), LWIP_EVENT_RECV, (p), 0, (err))
#define TCP_EVENT_CLOSED(pcb, ret) ret = lwip_tcp_event((pcb)->callback_arg, (pcb), LWIP_EVENT_RECV, NULL, 0, ERR_OK)
#define TCP_EVENT_CONNECTED(pcb, err, ret) \
    ret = lwip_tcp_event((pcb)->callback_arg, (pcb), LWIP_EVENT_CONNECTED, NULL, 0, (err))
#define TCP_EVENT_POLL(pcb, ret)                                                                \
    do                                                                                          \
    {                                                                                           \
        if ((pcb)->state != SYN_RCVD)                                                           \
        {                                                                                       \
            ret = lwip_tcp_event((pcb)->callback_arg, (pcb), LWIP_EVENT_POLL, NULL, 0, ERR_OK); \
        }                                                                                       \
        else                                                                                    \
        {                                                                                       \
            ret = ERR_ARG;                                                                      \
        }                                                                                       \
    } while (0)
/* For event API, last state SYN_RCVD must be excluded here: the application
   has not seen this pcb, yet! */
#define TCP_EVENT_ERR(last_state, errf, arg, err)                        \
    do                                                                   \
    {                                                                    \
        if (last_state != SYN_RCVD)                                      \
        {                                                                \
            lwip_tcp_event((arg), NULL, LWIP_EVENT_ERR, NULL, 0, (err)); \
        }                                                                \
    } while (0)

#else /* LWIP_EVENT_API */

#define TCP_EVENT_ACCEPT(lpcb, pcb, arg, err, ret)       \
    do                                                   \
    {                                                    \
        if ((lpcb)->accept != NULL)                      \
            (ret) = (lpcb)->accept((arg), (pcb), (err)); \
        else                                             \
            (ret) = ERR_ARG;                             \
    } while (0)

#define TCP_EVENT_SENT(pcb, space, ret)                               \
    do                                                                \
    {                                                                 \
        if ((pcb)->sent != NULL)                                      \
            (ret) = (pcb)->sent((pcb)->callback_arg, (pcb), (space)); \
        else                                                          \
            (ret) = ERR_OK;                                           \
    } while (0)

#define TCP_EVENT_RECV(pcb, p, err, ret)                                 \
    do                                                                   \
    {                                                                    \
        if ((pcb)->recv != NULL)                                         \
        {                                                                \
            (ret) = (pcb)->recv((pcb)->callback_arg, (pcb), (p), (err)); \
        }                                                                \
        else                                                             \
        {                                                                \
            (ret) = tcp_recv_null(NULL, (pcb), (p), (err));              \
        }                                                                \
    } while (0)

#define TCP_EVENT_CLOSED(pcb, ret)                                         \
    do                                                                     \
    {                                                                      \
        if (((pcb)->recv != NULL))                                         \
        {                                                                  \
            (ret) = (pcb)->recv((pcb)->callback_arg, (pcb), NULL, ERR_OK); \
        }                                                                  \
        else                                                               \
        {                                                                  \
            (ret) = ERR_OK;                                                \
        }                                                                  \
    } while (0)

#define TCP_EVENT_CONNECTED(pcb, err, ret)                               \
    do                                                                   \
    {                                                                    \
        if ((pcb)->connected != NULL)                                    \
            (ret) = (pcb)->connected((pcb)->callback_arg, (pcb), (err)); \
        else                                                             \
            (ret) = ERR_OK;                                              \
    } while (0)

#define TCP_EVENT_POLL(pcb, ret)                             \
    do                                                       \
    {                                                        \
        if ((pcb)->poll != NULL)                             \
            (ret) = (pcb)->poll((pcb)->callback_arg, (pcb)); \
        else                                                 \
            (ret) = ERR_OK;                                  \
    } while (0)

#define TCP_EVENT_ERR(last_state, errf, arg, err) \
    do                                            \
    {                                             \
        LWIP_UNUSED_ARG(last_state);              \
        if ((errf) != NULL)                       \
            (errf)((arg), (err));                 \
    } while (0)

#endif /* LWIP_EVENT_API */

/** Enabled extra-check for TCP_OVERSIZE if LWIP_DEBUG is enabled */
#if TCP_OVERSIZE && defined(LWIP_DEBUG)
#define TCP_OVERSIZE_DBGCHECK 1
#else
#define TCP_OVERSIZE_DBGCHECK 0
#endif

/** Don't generate checksum on copy if CHECKSUM_GEN_TCP is disabled */
#define TCP_CHECKSUM_ON_COPY (LWIP_CHECKSUM_ON_COPY && CHECKSUM_GEN_TCP)

    /* This structure represents a TCP segment on the unsent, unacked and ooseq queues */
    struct tcp_seg
    {
        struct tcp_seg* next; /* used when putting segments on a queue */
        struct pbuf* p;       /* buffer containing data + TCP header */
        u16_t len;            /* the TCP length of this segment */
#if TCP_OVERSIZE_DBGCHECK
        u16_t oversize_left; /* Extra bytes available at the end of the last
                                pbuf in unsent (used for asserting vs.
                                tcp_pcb.unsent_oversize only) */
#endif                       /* TCP_OVERSIZE_DBGCHECK */
#if TCP_CHECKSUM_ON_COPY
        u16_t chksum;
        u8_t chksum_swapped;
#endif /* TCP_CHECKSUM_ON_COPY */
        u8_t flags;
#define TF_SEG_OPTS_MSS (u8_t)0x01U /* Include MSS option (only used in SYN segments) */
#define TF_SEG_OPTS_TS  (u8_t)0x02U /* Include timestamp option. */
#define TF_SEG_DATA_CHECKSUMMED                                           \
    (u8_t)0x04U                           /* ALL data (not the header) is \
                                             checksummed into 'chksum' */
#define TF_SEG_OPTS_WND_SCALE (u8_t)0x08U /* Include WND SCALE option (only used in SYN segments) */
#define TF_SEG_OPTS_SACK_PERM (u8_t)0x10U /* Include SACK Permitted option (only used in SYN segments) */
        struct tcp_hdr* tcphdr;           /* the TCP header */
    };

#define LWIP_TCP_OPT_EOL       0
#define LWIP_TCP_OPT_NOP       1
#define LWIP_TCP_OPT_MSS       2
#define LWIP_TCP_OPT_WS        3
#define LWIP_TCP_OPT_SACK_PERM 4
#define LWIP_TCP_OPT_TS        8

#define LWIP_TCP_OPT_LEN_MSS   4
#if LWIP_TCP_TIMESTAMPS
#define LWIP_TCP_OPT_LEN_TS     10
#define LWIP_TCP_OPT_LEN_TS_OUT 12 /* aligned for output (includes NOP padding) */
#else
#define LWIP_TCP_OPT_LEN_TS_OUT 0
#endif
#if LWIP_WND_SCALE
#define LWIP_TCP_OPT_LEN_WS     3
#define LWIP_TCP_OPT_LEN_WS_OUT 4 /* aligned for output (includes NOP padding) */
#else
#define LWIP_TCP_OPT_LEN_WS_OUT 0
#endif

#if LWIP_TCP_SACK_OUT
#define LWIP_TCP_OPT_LEN_SACK_PERM     2
#define LWIP_TCP_OPT_LEN_SACK_PERM_OUT 4 /* aligned for output (includes NOP padding) */
#else
#define LWIP_TCP_OPT_LEN_SACK_PERM_OUT 0
#endif

#define LWIP_TCP_OPT_LENGTH(flags)                                                                                    \
    ((flags) & TF_SEG_OPTS_MSS ? LWIP_TCP_OPT_LEN_MSS : 0) + ((flags) & TF_SEG_OPTS_TS ? LWIP_TCP_OPT_LEN_TS_OUT : 0) \
        + ((flags) & TF_SEG_OPTS_WND_SCALE ? LWIP_TCP_OPT_LEN_WS_OUT : 0)                                             \
        + ((flags) & TF_SEG_OPTS_SACK_PERM ? LWIP_TCP_OPT_LEN_SACK_PERM_OUT : 0)

/** This returns a TCP header option for MSS in an u32_t */
#define TCP_BUILD_MSS_OPTION(mss) lwip_htonl(0x02040000 | ((mss) & 0xFFFF))

#if LWIP_WND_SCALE
#define TCPWNDSIZE_F      U32_F
#define TCPWND_MAX        0xFFFFFFFFU
#define TCPWND_CHECK16(x) LWIP_ASSERT("window size > 0xFFFF", (x) <= 0xFFFF)
#define TCPWND_MIN16(x)   ((u16_t)LWIP_MIN((x), 0xFFFF))
#else /* LWIP_WND_SCALE */
#define TCPWNDSIZE_F U16_F
#define TCPWND_MAX   0xFFFFU
#define TCPWND_CHECK16(x)
#define TCPWND_MIN16(x) x
#endif /* LWIP_WND_SCALE */

    /* Global variables: */
    extern struct tcp_pcb* tcp_input_pcb;
    extern u32_t tcp_ticks;
    extern u8_t tcp_active_pcbs_changed;

    /* The TCP PCB lists. */
    union tcp_listen_pcbs_t { /* List of all TCP PCBs in LISTEN state. */
        struct tcp_pcb_listen* listen_pcbs;
        struct tcp_pcb* pcbs;
    };
    extern struct tcp_pcb* tcp_bound_pcbs;
    extern union tcp_listen_pcbs_t tcp_listen_pcbs;
    extern struct tcp_pcb* tcp_active_pcbs; /* List of all TCP PCBs that are in a
                 state in which they accept or send
                 data. */
    extern struct tcp_pcb* tcp_tw_pcbs;     /* List of all TCP PCBs in TIME-WAIT. */

#define NUM_TCP_PCB_LISTS_NO_TIME_WAIT 3
#define NUM_TCP_PCB_LISTS              4
    extern struct tcp_pcb** const tcp_pcb_lists[NUM_TCP_PCB_LISTS];

/* Axioms about the above lists:
   1) Every TCP PCB that is not CLOSED is in one of the lists.
   2) A PCB is only in one of the lists.
   3) All PCBs in the tcp_listen_pcbs list is in LISTEN state.
   4) All PCBs in the tcp_tw_pcbs list is in TIME-WAIT state.
*/
/* Define two macros, TCP_REG and TCP_RMV that registers a TCP PCB
   with a PCB list or removes a PCB from a list, respectively. */
#ifndef TCP_DEBUG_PCB_LISTS
#define TCP_DEBUG_PCB_LISTS 0
#endif
#if TCP_DEBUG_PCB_LISTS
#define TCP_REG(pcbs, npcb)                                                                                     \
    do                                                                                                          \
    {                                                                                                           \
        struct tcp_pcb* tcp_tmp_pcb;                                                                            \
        LWIP_DEBUGF(TCP_DEBUG, ("TCP_REG %p local port %" U16_F "\n", (void*)(npcb), (npcb)->local_port));      \
        for (tcp_tmp_pcb = *(pcbs); tcp_tmp_pcb != NULL; tcp_tmp_pcb = tcp_tmp_pcb->next)                       \
        {                                                                                                       \
            LWIP_ASSERT("TCP_REG: already registered\n", tcp_tmp_pcb != (npcb));                                \
        }                                                                                                       \
        LWIP_ASSERT("TCP_REG: pcb->state != CLOSED", ((pcbs) == &tcp_bound_pcbs) || ((npcb)->state != CLOSED)); \
        (npcb)->next = *(pcbs);                                                                                 \
        LWIP_ASSERT("TCP_REG: npcb->next != npcb", (npcb)->next != (npcb));                                     \
        *(pcbs) = (npcb);                                                                                       \
        LWIP_ASSERT("TCP_REG: tcp_pcbs sane", tcp_pcbs_sane());                                                 \
        tcp_timer_needed();                                                                                     \
    } while (0)
#define TCP_RMV(pcbs, npcb)                                                                          \
    do                                                                                               \
    {                                                                                                \
        struct tcp_pcb* tcp_tmp_pcb;                                                                 \
        LWIP_ASSERT("TCP_RMV: pcbs != NULL", *(pcbs) != NULL);                                       \
        LWIP_DEBUGF(TCP_DEBUG, ("TCP_RMV: removing %p from %p\n", (void*)(npcb), (void*)(*(pcbs)))); \
        if (*(pcbs) == (npcb))                                                                       \
        {                                                                                            \
            *(pcbs) = (*pcbs)->next;                                                                 \
        }                                                                                            \
        else                                                                                         \
            for (tcp_tmp_pcb = *(pcbs); tcp_tmp_pcb != NULL; tcp_tmp_pcb = tcp_tmp_pcb->next)        \
            {                                                                                        \
                if (tcp_tmp_pcb->next == (npcb))                                                     \
                {                                                                                    \
                    tcp_tmp_pcb->next = (npcb)->next;                                                \
                    break;                                                                           \
                }                                                                                    \
            }                                                                                        \
        (npcb)->next = NULL;                                                                         \
        LWIP_ASSERT("TCP_RMV: tcp_pcbs sane", tcp_pcbs_sane());                                      \
        LWIP_DEBUGF(TCP_DEBUG, ("TCP_RMV: removed %p from %p\n", (void*)(npcb), (void*)(*(pcbs))));  \
    } while (0)

#else /* LWIP_DEBUG */

#define TCP_REG(pcbs, npcb)   \
    do                        \
    {                         \
        (npcb)->next = *pcbs; \
        *(pcbs) = (npcb);     \
        tcp_timer_needed();   \
    } while (0)

#define TCP_RMV(pcbs, npcb)                                                                 \
    do                                                                                      \
    {                                                                                       \
        if (*(pcbs) == (npcb))                                                              \
        {                                                                                   \
            (*(pcbs)) = (*pcbs)->next;                                                      \
        }                                                                                   \
        else                                                                                \
        {                                                                                   \
            struct tcp_pcb* tcp_tmp_pcb;                                                    \
            for (tcp_tmp_pcb = *pcbs; tcp_tmp_pcb != NULL; tcp_tmp_pcb = tcp_tmp_pcb->next) \
            {                                                                               \
                if (tcp_tmp_pcb->next == (npcb))                                            \
                {                                                                           \
                    tcp_tmp_pcb->next = (npcb)->next;                                       \
                    break;                                                                  \
                }                                                                           \
            }                                                                               \
        }                                                                                   \
        (npcb)->next = NULL;                                                                \
    } while (0)

#endif /* LWIP_DEBUG */

#define TCP_REG_ACTIVE(npcb)             \
    do                                   \
    {                                    \
        TCP_REG(&tcp_active_pcbs, npcb); \
        tcp_active_pcbs_changed = 1;     \
    } while (0)

#define TCP_RMV_ACTIVE(npcb)             \
    do                                   \
    {                                    \
        TCP_RMV(&tcp_active_pcbs, npcb); \
        tcp_active_pcbs_changed = 1;     \
    } while (0)

#define TCP_PCB_REMOVE_ACTIVE(pcb)             \
    do                                         \
    {                                          \
        tcp_pcb_remove(&tcp_active_pcbs, pcb); \
        tcp_active_pcbs_changed = 1;           \
    } while (0)

    /* Internal functions: */
    struct tcp_pcb* tcp_pcb_copy(struct tcp_pcb* pcb);
    void tcp_pcb_purge(struct tcp_pcb* pcb);
    void tcp_pcb_remove(struct tcp_pcb** pcblist, struct tcp_pcb* pcb);

    void tcp_segs_free(struct tcp_seg* seg);
    void tcp_seg_free(struct tcp_seg* seg);
    struct tcp_seg* tcp_seg_copy(struct tcp_seg* seg);

#define tcp_ack(pcb)                            \
    do                                          \
    {                                           \
        if ((pcb)->flags & TF_ACK_DELAY)        \
        {                                       \
            tcp_clear_flags(pcb, TF_ACK_DELAY); \
            tcp_ack_now(pcb);                   \
        }                                       \
        else                                    \
        {                                       \
            tcp_set_flags(pcb, TF_ACK_DELAY);   \
        }                                       \
    } while (0)

#define tcp_ack_now(pcb) tcp_set_flags(pcb, TF_ACK_NOW)

    err_t tcp_send_fin(struct tcp_pcb* pcb);
    err_t tcp_enqueue_flags(struct tcp_pcb* pcb, u8_t flags);

    void tcp_rexmit_seg(struct tcp_pcb* pcb, struct tcp_seg* seg);

#if LWIP_TCP_TC8_RST_NACK
    void tcp_rst_no_ack(
        const struct tcp_pcb* pcb,
        u32_t seqno,
        u32_t ackno,
        const ip_addr_t* local_ip,
        const ip_addr_t* remote_ip,
        u16_t local_port,
        u16_t remote_port);
#endif /* LWIP_TCP_TC8_RST_NACK */

    void tcp_rst(
        const struct tcp_pcb* pcb,
        u32_t seqno,
        u32_t ackno,
        const ip_addr_t* local_ip,
        const ip_addr_t* remote_ip,
        u16_t local_port,
        u16_t remote_port);

    u32_t tcp_next_iss(struct tcp_pcb* pcb);

    err_t tcp_keepalive(struct tcp_pcb* pcb);
    err_t tcp_split_unsent_seg(struct tcp_pcb* pcb, u16_t split);
    err_t tcp_zero_window_probe(struct tcp_pcb* pcb);
    void tcp_trigger_input_pcb_close(void);

#if TCP_CALCULATE_EFF_SEND_MSS
    u16_t tcp_eff_send_mss_netif(u16_t sendmss, struct netif* outif, const ip_addr_t* dest);
#define tcp_eff_send_mss(sendmss, src, dest) tcp_eff_send_mss_netif(sendmss, ip_route(src, dest), dest)
#endif /* TCP_CALCULATE_EFF_SEND_MSS */

#if LWIP_CALLBACK_API
    err_t tcp_recv_null(void* arg, struct tcp_pcb* pcb, struct pbuf* p, err_t err);
#endif /* LWIP_CALLBACK_API */

#if TCP_DEBUG || TCP_INPUT_DEBUG || TCP_OUTPUT_DEBUG
    void tcp_debug_print(struct tcp_hdr* tcphdr);
    void tcp_debug_print_flags(u8_t flags);
    void tcp_debug_print_state(enum tcp_state s);
    void tcp_debug_print_pcbs(void);
    s16_t tcp_pcbs_sane(void);
#else
#define tcp_debug_print(tcphdr)
#define tcp_debug_print_flags(flags)
#define tcp_debug_print_state(s)
#define tcp_debug_print_pcbs()
#define tcp_pcbs_sane() 1
#endif /* TCP_DEBUG */

    /** External function (implemented in timers.c), called when TCP detects
     * that a timer is needed (i.e. active- or time-wait-pcb found). */
    void tcp_timer_needed(void);

    void tcp_netif_ip_addr_changed(const ip_addr_t* old_addr, const ip_addr_t* new_addr);

#if TCP_QUEUE_OOSEQ
    void tcp_free_ooseq(struct tcp_pcb* pcb);
#endif

#if LWIP_TCP_PCB_NUM_EXT_ARGS
    err_t tcp_ext_arg_invoke_callbacks_passive_open(struct tcp_pcb_listen* lpcb, struct tcp_pcb* cpcb);
#endif

#ifdef __cplusplus
}
#endif

#endif /* LWIP_TCP */

#endif /* LWIP_HDR_TCP_PRIV_H */
